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installing hardy backer board around a tub

Cementitious backerboard will wick moisture, so I'd suggest leaving about 1/4" from the tub surface to the bottom edge of the backer. Be sure it overlaps the lip of the tub. Once the backer and tile are up, you'll caulk this gap with bathroom silicone.

Be sure that the backerboard joints are being taped and mudded with thinset and tilebacker tape, and the backerboard is being properly waterproofed with an applied coating prior to tiling...Both are critical steps to a good installation.

installing hardy backer board around a tub

Quote:

Originally Posted by thekctermite

Cementitious backerboard will wick moisture, so I'd suggest leaving about 1/4" from the tub surface to the bottom edge of the backer. Be sure it overlaps the lip of the tub. Once the backer and tile are up, you'll caulk this gap with bathroom silicone.

Be sure that the backer board joints are being taped and mudded with thinset and tilebacker tape, and the backerboard is being properly waterproofed with an applied coating prior to tiling...Both are critical steps to a good installation.

I have to disagree some what with bring the backer over the lip. I have been installing the backer for years so the backer sits on top of the lip then caulking it and then thin setting all joints. when you go to install the tile fill the gap with thin-set and then install the tile straight down on top of the tub. leaving a small gap the size of a four penny finish nail for grout and caulk. when your remolding $60,000 dollar bath rooms the one thing the home owner or interior decorator does not want to see is an uneven tiled wall. sorry guy's . Just my procedure.
If your going to do it over the lip then your going to have to fur the walls out to make the lip flush with the framing.

installing hardy backer board around a tub

Quote:

Originally Posted by buletbob

the one thing the home owner or interior decorator does not want to see is an uneven tiled wall. If your going to do it over the lip then your going to have to fur the walls out to make the lip flush with the framing.

I agree that it is an ugly eye catcher to see the bottom row of tiles kick out because the backer board has been installed over a 1/4" thick tub lip. However, I prefer to bring the backer to within 3/16" of the tub surface and seal this joint with silicone before tiling as a cheap insurance to help prevent moisture wicking up the backer. I prefer this to just backfilling with thinset, so that when the tub/tile joint begins to leak, and we all know it positively will, the thinset cannot wick water up to the backer and set up a long term hidden moisture problem. My solution is to mark out about a 3" wide notch across the studs the tub crosses, then with a mortising bit in a router, set to the depth of the tub lip thickness, I create a pocket so the tub lip will be flush with the face of the studs. It takes less than 1/2 hour to do this, half of that being the time to notch the corner studs, which I do with a chisel. Much easier than furring walls out, leaves no room for argument from the plumber, and no excuses for the tile man not to have a flat wall; so now I can use that time convincing him not to fill the tile/tub joint with grout, but rather with color matched caulk.

Last edited by troubleseeker; 08-06-2008 at 08:23 PM.

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installing hardy backer board around a tub

Quote:

Originally Posted by buletbob

I have to disagree some what with bring the backer over the lip. I have been installing the backer for years so the backer sits on top of the lip then caulking it and then thin setting all joints. when you go to install the tile fill the gap with thin-set and then install the tile straight down on top of the tub. leaving a small gap the size of a four penny finish nail for grout and caulk. when your remolding $60,000 dollar bath rooms the one thing the home owner or interior decorator does not want to see is an uneven tiled wall. sorry guy's . Just my procedure.
If your going to do it over the lip then your going to have to fur the walls out to make the lip flush with the framing.

Totally agree.. this is how we finish our backerboard and tile as well.. works every time. We use denshield and seal all our seams with kerdi membrane material

installing hardy backer board around a tub

Does this diagram show your installation properly? Is the empty area under the Denshield backer filled with thinset? Or, do you silicon caulk the Denshild/tub flange junction and then fill with thinset when you'rs tiling?

installing hardy backer board around a tub

Stop the backerboard just above the tub lip, then seal the joint with silicone sealer. Dropping the backer over the lip will cause it to "kick" at the bottom, thus also kicking out the bottom edge of the tiles. While most laymen will not percieve this, it will be obvious to any trained professional eye, particularly at the vertical corners. Use spacers to maintain a consistent gap between the bottom tile and the tub; fill with sealant, not grout which will quickly crack and fall out due to the movement of this joint.
I used to spend time notching the tub lip into the studs, but have changed that in an effort to be less anal.